1. Field of the Invention
The invention relates to a lens device, more particularly to a lens device capable of blocking unnecessary light.
2. Description of the Related Art
As shown in FIGS. 1 and 2, a conventional lens device 10 is zoom adjustable along an axis (L), and is adapted for use with a digital camera. The conventional lens device 10 includes a base 11, a focus lens unit 12, a focus driving unit 13, a main barrel 14, a first cam barrel 15, a first lens unit 16, and a second lens unit 17. The digital camera includes an image sensing component 100 disposed on the base 11 and aligned with the focus lens unit 12 along the axis (L).
The focus lens unit 12 is mounted movably to the base 11. The focus driving 13 is mounted to the base 11 and is operable to drive the focus lens unit 12 to move along the axis (L). The main barrel 14 is slidably connected to a second cam barrel 153 mounted to the base 11, and has an inner annular surface 141, three first guide slots 142 (only one is shown) extending parallel to the axis (L), and three second guide slots 143 (only one is shown) extending parallel to the axis (L). The first cam barrel 15 is sleeved rotatably on the main barrel 14, and is formed with three first cam slots 151 (only one is shown) and three second cam slots 152 (only one is shown).
The first lens unit 16 is sleeved in the main barrel 14, and includes a first lens frame 160, a plurality of first lenses 161 secured to the first lens frame 160, and three first connecting pins 162 (only one is shown) extending respectively through the first guide slots 142 and retained slidably and respectively in the first cam slots 151. The second lens unit 17 is sleeved in the main barrel 14, and includes a second lens frame 170, a plurality of second lenses 171 secured to the second lens frame 170, and three second connecting pins 172 (only one is shown) extending respectively through the second guide slots 143 and retained slidably and respectively in the second cam slots 152. The image sensing component 100 of the digital camera is aligned with the first and second lenses 161, 171 along the axis (L).
The first cam barrel 15 can be driven to move rotatably along the axis (L) by a motor 191 and a driving unit 192 through a rotary drive barrel 193. The main barrel 14 that is sleeved inside the second cam barrel 153 will then be driven to move along the axis (L) by the first cam barrel 15. Since the first connecting pins 162 of the first lens unit 16 are retained respectively in the first cam slots 151 in the first cam barrel 15, and since the second connecting pins 172 of the second lens unit 17 are retained respectively in the second cam slots 152 in the first cam barrel 15, the first and second lenses 161, 171 will also move along the axis (L), thereby resulting in zoom adjustment.
However, when the first and second lens units 151, 152 move to an extended position (see FIG. 1), where the second lens unit 17 moves in a direction away from the focus lens unit 12, the focus lens unit 12 and the focus driving unit 13 will cooperatively define a first gap 18 therebetween, and the first and second lens units 16, 17 will cooperatively define a second gap 181. Therefore, ambient light (as indicated by the arrows in FIG. 1) can pass through the first lenses 161 of the first lens unit 16 and the second gap 181, be reflected by the inner annular surface 141 of the main barrel 14, and finally reach the image sensing component 100 via the first gap 18, thereby resulting in poor image quality.